Environmental Exposure In First Year Of Life Increases Asthma Risk

SEATTLE -- Exposure to cockroaches, the farming environment, wood smoke, pesticides and herbicides during the first year of life increases the risk of developing asthma later in childhood, according to a study presented at the American Thoracic Society International Conference in Seattle. "Environmental exposures early in life appear to be important for the development of asthma during childhood," said lead investigator Frank Gilliland, M.D., Ph.D., Professor of Preventive Medicine at the University of Southern California in Los Angeles. "Scientists have spent a lot of time looking at the role of indoor allergens, daycare attendance, and infections in asthma development. Many studies are focusing on events during the first year or two of life, but there has not been a careful look at other environmental exposures."

Dr. Gilliland studied more than 700 children, half of whom had developed asthma by age 5, and half who did not have asthma by age 5. Parents provided information on the children's early life environmental exposures. Dr. Gilliland found that children exposed to cockroaches within the first year of life were twice as likely as those not exposed to cockroaches to develop asthma.

Herbicide exposure in the first year of life was associated with a 4.6-fold increased risk of asthma, while pesticide exposure was associated with a 2.4-fold increased risk.

"We also found that exposure to wood or oil smoke in home from heating and exposures to the farming environment increased the risk of asthma, but the risk was strongest if the exposures occurred in the first year of life, said Dr. Gilliland. "If the exposure occurred when the child was older, it didn't have as large an effect."

In the first year of a child's life, the lungs are rapidly growing and the immune system is developing, so the child is particularly likely to become sensitized to asthma triggers, Dr. Gilliland said. "Infants are different than older children or adults--their behavior patterns are different. Their respiratory rates are higher, and their ability to metabolize and excrete materials from the environment is different. The increased risk for asthma that we noted from environmental exposures during the first year may reflect that sensitive window in development.